I seem to be having the same issue as everyone else in particular just like dhowell626 I have just got my computer back from repair in the UK. The repair was to replace the entire outer casing (ie should not have impacted any software but I know they ran various diagnostic tests for good measure - they said 5 hours of tests).
When I switched on my MacBook Pro in the shop to check everything was OK I immediately started getting exactly the same symptoms: windows asking whether I wanted to allow or deny connection by configd and mDNSResponder, failure to connect to network with self assigned IP address, a new program called nmdb showing on the allowed list on my firewall. I had never experienced any of these problems before. Inspecting the log at the time when internet access was blocked shows that both configd and mDNSResponder were blocked at the same time as I was unable to get online. There does seem to be a strong connection here.
The Genius at the Mac store at first tried to deny it could be anything to do with what they have done as it was just a hardware job. He then suggested I just turn off the firewall saying "it's not that vulnerable if you allow all incoming network communications". This is definitely NOT my understanding and any quick research online will show the perils of switching off firewalls and I pointed this out. The Genius has agreed to take the machine back in again to replace the casing again (the new one was warped) and also to fix this problem. He thought a reinstallation of some part of the system would be needed to fix this problem.
In the meantime I have tried out the solution suggested by Heinrich with specific details supplied by lstnmysphr in this thread. Thank you very much for these suggestions; I could follow them and they seem to be working and this has enabled me to have the firewall up but specifically allowing config and mDNSResponder. I must say I am still unhappy about this. If nothing else, I did not need to do this before my Mac was taken in for repair and I am worried maybe other things have gone wrong as yet undiscovered. I shall therefore still be asking the Apple store to effect a proper repair of this issue that aparently was (most likely inadvertently) caused during their repair work.
Incidentally, the potential solution suggested by Simon69 did not match my symptoms. com.apple.kerberos.kdc and com.apple.systemdefault were both in my keychain.
I note in
http://docs.info.apple.com/article.html?artnum=306938 where Mac describe the updated firewall, they describe configd, mDNSResponder and a third service called racoon as being the only 3 "essential services" that continue to be permitted even under firewall option 2 ("Allow only essential services"). It suggests there is some glitch in the special permissions given to these services by the firewall, triggered maybe by battery resets, system time resets, or something else that happens when Macs are repaired and their casings are interfered with/replaced:
+2. Allow only essential services:+
+This is the most conservative mode. Mac OS X will block all connections except a limited list of services essential to the operation of your computer.+
+The system services that are still allowed to receive incoming connections are:+
+configd, which implements DHCP and other network configuration services+
+mDNSResponder, which implements Bonjour+
+racoon, which implements IPSec+
Given the very high number of visits to this thread (albeit limited posts there are nearly 2,000 viewings already) I suspect lots of people are having this problem. It seems to be relatively recent and may be connected to the updates to Leopard that modified the firewall, or at least the descriptions of the firewall options.
It would therefore be great to see Apple address this issue, give us some clarification and potentially release a bug fix. For those of us who have applied these patches, please let us know whether we've done the right thing and/or should take any further action.
Charles
[This issue also seems to be connected to a posting in the Mac OS » Mac OS X v10.5 Leopard » Getting Online and Networking forum Re: Self Assigning IP Issue although I do not think that thread adds much additional to the discussion in this thread. One common theme may be around resetting system dates. Replacing batteries evidently does this and it's possible certain repairs or diagnostics done by Apple repairers may do something similar too.]
